If you were thinking of maybe going out after work today and giving ziplining a shot, but replacing a standard safety harness and pulley setup with a simple t-shirt…don’t. It’s a bad idea.

Last saturday night in New Jersey, a bunch of kids were playing soccer on the field at Glen Rock High School when one of them—an unnamed 15-year-old—noticed the school had a zip line and decided to give it a try. However, he didn’t have a harness or a pulley, so instead he used what his genius brain determined to be the next best thing: his cotton t-shirt.

Now, you don’t have to be a mechanical engineer to know that cotton is probably not going to slide too smoothly across a steel wire. But this 15-year-old was having none of that common sense business, so he tried ziplining with his t-shirt and got stuck 30 feet in the air.

Then—and this is maybe the best part—when his friends on the ground told him they would catch him if he let go, he believed them. And that resulted in a broken femur and some sort of unspecified foot injury.

Take a look:

Some parents say the zipline should be more secure or take the zipline down altogether. But I’m pretty sure the rest of us think some parents should teach their kids about gravity.

Keep the zipline, Glen Rock. Idiots are always going to find a way to be idiots.